Controversial reforms to public sector pensions are unlikely to save the government money over the longer term, according to analysis by the Institute of Fiscal Studies (IFS).

The reforms include a switch from final salary schemes to pensions based on career average earnings, an increase in contributions by members, a retirement age pegged to the state pension age, and switching the way pensions are increased each year from RPI to the lower CPI.

Negotiations between the government and unions are ongoing, but have already led to strikes by members of 29 unions including teachers, hospital employees, paramedics, council staff and other civil servants at the end of November 2011.

The government said the intention of the reforms was to improve fairness and control the cost of these schemes, which are estimated to cost the taxpayer £32bn a year and provide pensions far superior to those earned by most people in the private sector.

But the IFS analysis indicates that while the move from RPI to CPI indexation will substantially reduce expected costs and generosity of pensions paid out to retired members, reforms to the structure of the schemes will make little difference to the long-term costs.

The think-tank said that, in general, lower earners in the public sector would get a more generous pension as a result of the reforms, being able to retire at age 65 with a higher annual pension than they would receive under current arrangements.

This is because staff earning less than £15,000 will be exempt from increased contributions, and the move from final salary to career average schemes includes improvements to accrual rates, which control the amount of money attributed to a member's pension pot each year.

Conversely, higher earners are likely to lose out. The move from final salary to career average relatively penalises those who see big increases in their earnings over time, particularly towards the end of their career.

The IFS said that by increasing the generosity to lower earners – a group less likely to have a good occupational pension in the private sector – the reforms increase the difference between pension provision in the public and the private sectors.

Carl Emmerson, deputy director of the IFS and co-author of the paper, said: "The reforms to public service pensions implemented by the last Labour government, and this government's decision to switch from RPI to CPI indexation of pension benefits, will in the long run reduce the generosity and therefore the cost of these schemes to the taxpayer.

"But the consequence of the long drawn-out negotiations over the latest [structural] reform appears to be little or no long-term saving to the taxpayer or reduction in generosity, on average, of pensions for public service workers."

However the TUC's general secretary, Brendan Barber, refuted the IFS analysis, saying it examined only one of the three major changes to public sector pensions: "If you take the package as a whole there can be no doubt that many public sector workers may have to pay more, work longer and get a pension that will not keep up with the proper measure of the cost of living."